1. Technical Field
The present invention relates to a semiconductor integrated circuit, and more particularly, to a current control apparatus and a phase change memory having the same.
2. Related Art
Nonvolatile memory apparatuses maintain stored data even though power supply is cut off. Therefore, the nonvolatile memory apparatuses are widely adopted in computers, mobile telecommunication systems, memory cards, and so on.
A representative example of the nonvolatile memory apparatus is flash memory. The flash memory adopts a memory cell structure such as a stacked gate structure. In such a flash memory, a film quality of a tunnel oxide layer should be improved, and a coupling ratio between cells should be increased, in order to enhance the reliability and program efficiency of flash memory cells.
Currently, a phase change memory apparatus having a random access property of DRAM is being developed as a replacement for flash memory.
In general, a phase change memory apparatus includes a plurality of word lines, a plurality of bit lines arranged in such a manner as to intersect the plurality of word lines, and a plurality of phase change memory cells in the respective intersection points between the word lines and the bit lines.
Each of the phase change memory cells includes a switching element coupled to a word line and a variable resistor element coupled between the switching element and a bit line. The variable resistor element may be formed of a phase change material whose resistance value changes according to the amount of current provided.
Referring to FIG. 1, the phase change material used as the variable resistor element of the phase change memory cell is characterized in that the resistance value changes with temperature. Therefore, the phase change material has a relatively low resistance value at high temperature and a relatively high resistance value at low temperature. Accordingly, while the property change of the phase change material used as the variable resistor material at high temperature is larger than at a nominal temperature, the property change at low temperature is smaller than at the nominal temperature. The nominal temperature may be, for example, 70° F. Therefore, the resistance value of the phase change material may not be consistent for a predetermined program pulse because the degree of the property change differs depending on temperature. In this case, a data storage error may occur depending on the temperature at the time of storage.